19121-64-3Relevant academic research and scientific papers
Hydrogen atom abstraction from hexamethyl(Dewar benzene), hexamethylprismane, and a 1,3-hydrogen-shifted isomer of hexamethylbenzvalene. A study by electron paramagnetic resonance spectroscopy
Effio, A. A.,Ingold, K. U.
, p. 96 - 98 (1981)
Photochemically generated tert-butoxyls abstract an allylic hydrogen atom from hexamethyl(Dewar benzene).The resultant allylic radical 4, aH(2 H) = 12.40 G, aH(3 H) = 15.48 G> can be observed from 150 to 375 K.T
Kinetics of the reaction of the TEMPO radical with alkylarenes
Opeida,Matvienko,Bakurova,Voloshkin
, p. 900 - 904 (2007/10/03)
The kinetics of the reaction of the stable radical 2,2,6,6- tetramethylpiperidine-N-oxyl (TEMPO) with a series of alkylarenes containing primary and secondary benzyl C-H bonds was studied by ESR, and the reaction rate constants were determined. The scheme
Laser photolysis investigation of induced quenching in photoreduction of benzophenone by alkylbenzenes and anisoles
Oekada, Kafsuji,Yamaji, Minora,Smzuka, Haruo
, p. 861 - 866 (2007/10/03)
The quenching processes of triplet benzophenone (JBP) by alkylbenzenes (AB) and anisole derivatives (AD) in benzene (Bz) and a mixture of acetonitriie (ACT-,) and water (4 :1 v/V; have been studied on the basis of rate constants and efficiencies determined by nanosecond laser flash photolysis a; 355 n m at 295 K. It was found that (1) the deactivation of 3BPby ADs in ACN H2O (4 :1 v/v) was governed by electron transfer (ET) to produce the benzophenone anion (BP'~) and corresponding cation (AD' + ) radicals wiih efficiencies, atj 1 whereas no chemical species were formed in Bz; and 2) photoreduction of 3BPby ABs resulted in benzophenone ketyl radical (BPK) formation by benzylic hydrogen abstraction (HA) with efficiencies XHA 1 in 3z and ACN-H2O (4 :1 v/v). The residual efficiency (a: 1 -ET or ! -aH/1) was attributed to a birnolecular process with no photochemical product, which was named 'induced-quenching (IQf. The quenching rate constants (Jcq) of ;'BPby ADs and ABs were less than the diffusion limits of both Bz and AC1~H2O (4 :1 v/v). The net bimolecular rate constants for the ET, HA and IQ processes were estimated from the k values and efficiencies. The rate constants (%T and k,Q) of ET and IQ with AD versus the oxidation potential (￡) of AD followed Rchm-Weller behaviour while logarithmic rate constants {/CHA and ki(j) of HA and IQ by ABs increased linearly with a decrease in the Em of AB. It was suggested, for the deactivation mechanism of 3BPby ABs and ADs (RH), that ;1) the IQ process was intersystem crossing (ISC) enhanced by the partial charge transfer (CT) character of the triplet excipiexes, 3(BP"~- A-RHa + )a,e; (2) radical ion formation by ET might be accomplished in a polar solvent by further CT interaction in the excipiex; (3) the process of BPK formation was inferred to be H-atom transfer in the exciplex, where the more protic H-atom was readily mobile, rather than ET followed by proton transfer and (4) the loss of efficiencies of photochemicalproduct formation was derived not from back ET but from the IQ process, inherent to photoreactions, via triplet excipiexes. The deactivation processes of 3BPby RH are illustrated in Scheme 1. I ET BP'- + RH'(3BP' + RHJcoj -3(BPO- RHg,.-BPK 4 R' BP + RH Scheme 1.
Bromine Atom Complexes with Bromoalkanes. Their Formation in the Pulse Radiolysis of Di-, Tri-, and Tetrabromomethane and Their Reactivity with Organic Reductants
Shoute, Lian C. T.,Neta, P.
, p. 2447 - 2453 (2007/10/02)
Bromine atoms were produced in the pulse radiolysis of neat dibromomethane (DBM) and bromoform and of cyclohexane solutions containing DBM, bromoform, carbon tetrabromide, or ethyl bromide.The Br atoms form complexes with dimethyl sulfoxide (λmax 425 nm), with aromatic compounds, and with oxygen-containing compounds.In the absence of other complexing agents, since Br atoms do not abstract H from the solvents rapidly, they form complexes with their parent bromo compounds.The absorption maxima of these complexes are at 365 nm for C2H5Br*Br, 390 nm for CH2Br2*Br, 425 nm for CHBr3*Br, and 480 nm for CBr4*Br.The stability of RBr*Br appears to increase with the number of Br atoms in the molecule.These complexes act as oxidants towards p-methoxyphenol, 1,3,5-trimethoxybenzene, triphenylamine, and N,N,N',N'-tetramethyl-p-phenylenediamine.The cate constants for the oxidations were about 1E10 M-1 s-1 with CH2Br2*Br but only of the order of 1E8 - 1E9 M-1 s-1 with CBr4*Br.The initial products of the oxidation are the ion pairs between the radical cation of the organic substrate and the Br- ion.In the case of p-methoxyphenol the initial ion pair releases HBr under neutral or basic conditions to form the neutral p-methoxyphenoxyl radical.The Br atom complexes are also capable of abstracting H from weak C-H bonds.The benzylic and allylic hydrogens in hexamethylbenzene and cyclohexene are abstracted with rate constants near 1E9 by CH2Br2*Br and near 1E7 M-1 s-1 by CBr4*Br.The behavior of Br atoms is compared with that of Cl and I atoms.
